Method for melt spinning polycaprolactam into a low humidity environment

ABSTRACT

POLYCAPROLACTAM, DRIED TO A MOISTURE CONTENT OF LESS THAN 1%, IS MELT SPUN INTO AN ENCLOSURE IN WHICH RELATIVE HUMIDITY IS KEPT LESS THAN 50%. WHILE STILL WITHIN THE ENCLOSURE, A NON-AQUEOUS FINISHING COMPOSITION IS APPLIED TO THE FILAMENTS AFTER THEY SOLIDIFY. THE FILAMENTS ARE THEREAFTER, STILL IN SAID ENCLOSURE IN WHICH THE FILAMENTS ARE SHIELDED FROM HUMIDITY, AND WITHOUT ANY INTERMEDIATE COOLING OR AGING STEP, DRAWN WITH A DRAW RATIO OF GREATER THAN 5.0:1. THE RESULTING FILAMENTS HAVE A TENACITY ON THE ORDER OF 10 GRAMS PER DENIER.

Jan. 12, 1971 WATERS ETAL 3,555,139

METHOD FOR MELT SPINNING POLYCAPROLACTAM INTO A LOW HUMIDITY ENVIRONMENTOriginal Filed June 28. 1965 United States Patent O 3,555,139 METHOD FORMELT SPINNING POLYCAPROLAC- TAM INTO A LOW HUMIDITY ENVIRONMENT HerbertWaters, Chester, and Sterling M. Nichols, Hopewell, Va., assignors toThe Firestone Tire & Rubber Company, Akron, Ohio, a corporation of OhioContinuation of application Ser. No. 467,532, June 28, 1965. Thisapplication Aug. 20, 1969, Ser. No. 853,820 Int. Cl. D01d 5/12 US. Cl.264-210 2 Claims ABSTRACT OF THE DISCLOSURE Polycaprolactam, dried to amoisture content of less than 1%, is melt spun into an enclosure inwhich relative humidity is kept less than 50%. While still within theenclosure, a non-aqueous finishing composition is applied to thefilaments after they solidify. The filaments are thereafter, still insaid enclosure in which the filaments are shielded from humidity, andwithout any intermediate cooling or aging step, drawn with a draw ratioof greater than 5.0: 1. The resulting filaments have a tenacity on theorder of grams per denier.

This is continuation of SN. 467,532 filed June 28, 1965 and nowabandoned.

This invention relates to a process for the production of filaments frompolycaprolactam wherein the filaments are spun from a melt ofpolycaprolactam and directly thereafter, without intermediate windup orstorage, drawn to orient it to its final oriented-crystalline state.

Prospectively, the concept of direct spinning and drawing of nylon 6 todirectly form oriented-crystalline filaments would appear to be highlyattractive due to the presumable greater compactness of the equipmentand elimination of extra handling of the intermediate undrawn filament.However it has heretofore been considered that polycaprolactam filamentsrequired an aging time in undrawn state before being sujected to drawingto convert them to their final oriented-crystalline state, see A.Reichle and A. Prietzschk, Angewandte Chemie 74, 562569. It hastherefore heretofore been necessary to first melt spin thepolycaprolactam into unoriented filaments; to collect these filamentsupon bobbins; to store these bobbins for an extended aging time; totransfer these bobbins to drawing machines; and finally to draw thefilaments into final oriented-crystalline form. If this aging step wasomitted, it was impossible to draw the filaments beyond a ratio of ca.4.5 :1, and consequently impossible to attain desirably high degrees oftenacity, above say 7 grams/denier. The cumbersome nature of thisprocedure, involving considerable labor in the transfer and re-transferof the undrawn filament to and from storage, and the sprawling nature ofthe plant, with its separate spinning units, storage, and drawingmachinery, is very evident, but up to the present time unavoidable.

Accordingly it is an object of the invention to minimize the labor andhandling involved in the production of polycaprolactam filaments.

Another object is to provide a more compact plant for the manufacture ofpolycaprolactam filament than has heretofore been possible.

A further object is to provide a process for the manufacture ofpolycaprolactam filament wherein the filament is melt spun and theunoriented filaments continuously and directly taken from themelt-spinning operation to the drawing operation, without intermediatespooling and aging.

SYNOPSIS OF THE INVENTION The above and other objects are secured, inaccordance with this invention, in a process and apparatus wherein thepolycaprolactam, carefully dried to a moisture content less than 1%,based on the weight of the polycaprolactam plus moisture, is melt-spuninto an enclosure in which the relative humidity is kept extremely low,say less than 50% at room temperature, and a non-aqueous finishingcomposition is applied to the filaments as they solidify. The filamentsare thereafter, still in an enclosure in which the filaments areshielded from humidity, drawn with a draw ratio of greater than 5.0:1,say in the range of 5.4:1 to 7.5 :1. Under these conditions, which havebeen found to enable the high draw ratios cited even without an agingstep, filaments are obtained having tenacities on the order of 10 gramsper denier.

The invention is illustrated in the attached drawing, which is adiagrammatic view of an apparatus for the carrying out of thisinvention.

THE APPARATUS Referring more particularly to the drawing, there is showna reservoir and melter 10 into which polycaprolactam resin isintroduced, a pump 12 receiving the molten polycaprolactam from thereservoir 10 and spinning it out through a spinneret 14 into the form offilaments 16. The filaments 16 pass downwardly through an enclosingchimney 18 in a direction opposite to the flow of lowhumidity quenchingair indicated by the arrow 20. At the bottom of the chimney thefilaments impinge upon a revolving applicator roll 22 which applies anon-aqueous finishing liquid composition thereto, the finishingcomposition being supplied to the roll 22 by a pickup roll 24 bearingagainst the applicator roll and dipping into a trough 26 containing asupply of the finishing composition. From their impingement upon theapplicator roll, the filaments pass to a pair of heated and rotatingfeeding and braking rolls 28, 30 around which they are wrapped back andforth from roll 28 to roll 30 so that the speed of these rolls controlsthe speed of withdrawal of the filaments from the spinneret 14 and alsothe speed at which the filaments are fed to the further processing. Fromthe feeding rolls 28, 30, the filaments pass to a pair of heated,revolving drawing rolls 32, 34, around which they are wrapped back andforth, the rolls 32, 34 having a greater peripheral speed than the rolls28, 30, so that the filaments are drawn and stretch-oriented in theirreach 36 between the two sets of rolls. From the drawing rolls 32, 34the filaments are passed to a final windup (not shown) for storage andshipment. The feed and drawing rolls 28, 30, 32 and 34 are disposedwithin an enclosure 38, and during the passage through the enclosure anysolvents in the finishing agent applied at 22 is evaporated.

EXEMPLARY CONDITIONS OF OPERATION It 'will be understood that thespecific conditions of operation set out hereinbelow are given by way ofexample only, and that departures therefrom are permissible twithin thescope of the invention as set forth hereinbelow. In a typical run, thespinneret 14 had 204 orifices therein, each .010 in diameter by .015" inlength. The spinneret was operated at 515 F. 'with a throughput of 30lb./hr. of polycaprolactam. The chimney 18 was cylindrical in form andhad a height of 20 feet and a diameter of 8 inches. Air at F. and 45%relative humidity entered the apparatus at 40 and passed up the chimney18 and out at 42 at the rate of 35 cubic feet per minute. The finishingcomposition applied by the roll 22 was a solution comprising of adeodorized kerosene and 15% of Textolene 4018, (an anionic tire cord oilmanufactured by Sonneborn Chemical and Refining Company, Division ofWitco Chemical Company, Inc., having a Saybolt viscosity at 100 F. of960 seconds, a density of 7.9 lbs./ gal. Cloud point 20 F., Pour point lF. and pH in 5% solution of 7.5), the kerosene being substantiallycompletely evaporated during the passage of the filaments through theenclosure 38. The feed rolls 28, 30 are 6 inches in diameter and areoperated at 730 rpm. with an internal temperature of 240 F., thefilaments being wrapped 8 times therearound. The drawing rolls 32, 34are also 6 inches in diameter, are operated at 3825 r.p.m. with, aninternal temperature of 375 F., the filaments being Wrapped 18 timestherearound. The draw ratio is thus approximately 5.25: 1, and noexcessive breakage has been encountered. The product filaments had atenacity of 10 grams per denier. By way of contrast, if it is attemptedto operate with aqueous finishing agents and without shielding frommoisture and without aging, an impractical rate of breakage isencountered with draw ratios of this order of magnitude.

From the foregoing general discussion and detailed specific example ofthe carrying out of this invention, it will be evident that thisinvention provides a novel procedure whereby polycaprolactam may be meltspun and drawn into its final oriented crystalline form with high drawratios productive of high tenacities, all in a single unitary processand apparatus.

What is claimed is:

1. Process which comprises melting polycaprolactam which has previouslybeen dried to a moisture content of less than 1% spinning the moltenpolycaprolactam into filaments in an enclosure in which a flow ofcooling gas is maintained in a direction opposed to the direction ofmovement of said filaments, to cause said filaments to solidifymaintaining said cooling gas at a temperature of 75 F.

and a relative humidity of applying to said filaments a non-aqueousfinishing agent while still in said enclosure and without anyintermediate spooling or aging step passing said filaments, while stillwithin said enclosure and without any intermediate spooling or agingstep, over a set of draw rolls to draw said filaments to a draw ratio offrom 5.0:1 to 7.511.

2. Process according to claim 1 wherein said draw ratio is from 5.111 to7.0:1.

References Cited UNITED STATES PATENTS 2,733,122 1/1956 Herele et al264-2101 2,918,347 12/ 1959' Notarbartolo et a1. 264-2101 3,118,0121/1964 Kilian 2641 76F 3,156,750 11/1964 Cuculo 264-210F 3,317,980 5/1967 Jaeggli.

JULIUS FROME, Primary Examiner J. H. WOO, Assistant Examiner US. Cl.X.R.

